Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/85—Piezoelectric or electrostrictive active materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/85—Piezoelectric or electrostrictive active materials
  • H10N30/853—Ceramic compositions
  • H10N30/8548—Lead-based oxides
  • H10N30/8554—Lead-zirconium titanate [PZT] based
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G35/00—Compounds of tantalum
  • C01G35/006—Compounds containing, besides tantalum, two or more other elements, with the exception of oxygen or hydrogen
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/495—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates
  • C04B35/497—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates based on solid solutions with lead oxides
  • C04B35/499—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates based on solid solutions with lead oxides containing also titanates
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
  • H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
  • H10N30/077—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition
  • H10N30/078—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition by sol-gel deposition
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
  • H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
  • H10N30/079—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing using intermediate layers, e.g. for growth control
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/09—Forming piezoelectric or electrostrictive materials
  • H10N30/093—Forming inorganic materials
  • H10N30/097—Forming inorganic materials by sintering

Definitions

• the present invention relates to a piezoelectric PTZT film formed by a chemical solution deposition (CSD) method and a process for producing a liquid composition for forming the piezoelectric film.
• the present invention more specifically relates to a piezoelectric PTZT film having excellent piezoelectric properties, a long average breakdown time, and a high crystal-orientation degree, and a process for producing a liquid composition for forming the piezoelectric film.
• the piezoelectric PTZT film is a piezoelectric film of a piezoelectric PZT film having a perovskite structure including Pb, Zr, and Ti, in which some Ti and Zr are substituted with Ta.
• a PTZT precursor is a precursor of a piezoelectric PTZT film.
• Nb atoms may be trivalent, tetravalent, or pentavalent atoms
• the Nb atoms may be substituted for A-site ions as trivalent ions, even when it is intended that the Nb atoms are substituted for B-site ions as pentavalent ions.
• PTL 3 discloses a process for producing a ferroelectric thin film for forming an orientation-controlled layer in which crystalline orientation is controlled to the (100) plane on a lower electrode which will be described later.
• a method for manufacturing the piezoelectric film is provided.
• NPL 4 relates to phase formations and electrical properties of doped-PZT/PbTiOs films deposited by reactive sputtering using multi-targets. It is described that the tetragonality of PZT films is decreased with the Ta concentration and the surface morphology and grain size of PZT films are also changed with the content of Ta doping. Furthermore, it is reported that with increasing Ta doping the surface morphology of Ta doped PZT (PTZT) films is slightly smoothed and the grain sizes were considerably enlarged resulting in improved fatigue properties.
• An object of the present invention is to provide a piezoelectric PTZT film having excellent piezoelectric properties, a long average breakdown time, and a high crystal-orientation degree, and a process for producing a liquid composition for forming the piezoelectric film.
• the inventors have found from NPL 3 that, even when some Ti and Zr which are B-site ions of a metal oxide having a perovskite structure represented by ABO 3 including Pb, Zr, and Ti are intended to be substituted with Nb, the Nb atoms which may be trivalent, tetravalent, or pentavalent atoms may be substituted for A-site ions as trivalent ions. Accordingly, the inventors focused on Ta which has the same atomic radius as that of Nb and is more stable as a pentavalent atom.
• the inventors have found that, when some of Zr and Ti are substituted with Ta which is more stable as a pentavalent atom, and Ta alkoxide and Zr alkoxide are allowed to be reacted with a diol, at the time of synthesizing a precursor substance, to allow the carbon content to remain in a film at a given concentration during the process and to allow carbon to be suitably included in the film, it is possible to form a piezoelectric PTZT film having excellent piezoelectric properties, a long average breakdown time, and a high crystal-orientation degree, and thus, the inventors achieved the present invention.
• a piezoelectric PTZT film formed of a metal oxide having a perovskite structure including Pb, Ta, Zr, and Ti, in which the metal oxide further includes carbon, a content of the carbon is 80 to 800 ppm by mass, and a fraction of Ta atoms with respect to total metal atoms of Zr atoms and Ti atoms is in a range of 0 ⁇ Ta ⁇ 0.04.
• a process for producing a liquid composition for forming a piezoelectric PTZT film including: a step of preparing a first synthesis solution by refluxing a Ta alkoxide, a Zr alkoxide, ⁇ -diketones, and a diol to allow the Ta alkoxide and the Zr alkoxide to react with the diol; a step of preparing a second synthesis solution by adding a Ti alkoxide to the first synthesis solution to allow the refluxing and the reaction again; a step of preparing a third synthesis solution by adding a Pb compound to the second synthesis solution to further allow the refluxing and the reaction; and a step of preparing a fourth synthesis solution by removing a solvent from the third synthesis solution and diluting the solution with alcohol, in which, when the total amount of the Ta alkoxide, the Zr alkoxide, and the Ti alkoxide is set as 1 mole, the di
• a process for forming a piezoelectric PTZT film including: a step of forming a PTZT precursor film by applying the liquid composition for forming a piezoelectric PTZT film produced by the process according to the third aspect on an orientation-controlled film of a substrate and drying the liquid composition; a step of calcinating the PTZT precursor film; and a step of sintering the PTZT precursor film which is calcinated.
• an electronic component including the piezoelectric PTZT film according to the first or second aspect.
• the piezoelectric PTZT film according to the first aspect of the invention is produced by adding pentavalent Ta atoms into the metal oxide having a perovskite structure including Pb, Zr, and Ti.
• Ta is hardly substituted for A-site ions and is reliably substituted for some of Zr and Ti which are B-site ions.
• the metal oxide includes a predetermined amount of carbon. From these viewpoints, when the Ta atoms added are substituted for B-site, lead deficiency occurs in PZT, the movement of domains easily occurs, and therefore, a piezoelectric PTZT film having excellent piezoelectric properties, a long average breakdown time, and a high crystal-orientation degree is obtained.
• the fraction of the Ta atoms with respect to the total metal atoms of the Zr atoms and the Ti atoms is in a range of 0 ⁇ Ta ⁇ 0.04, a precipitate is hardly generated in the solution, when preparing a liquid composition for forming a piezoelectric PTZT film which will be described later.
• the piezoelectric PTZT film is formed from this liquid composition by refluxing a Ta alkoxide, a Zr alkoxide, ⁇ -diketones, and a diol to allow the Ta alkoxide and the Zr alkoxide to react with the diol in the step of preparing the first synthesis solution, a predetermined amount of carbon can be included in the piezoelectric film, and when a Ta alkoxide and a Zr alkoxide are compounded for stabilization, it is possible to prevent the generation of a precipitate and increase storage stability.
• the PTZT precursor film when the PTZT precursor film is formed by applying the liquid composition for forming a piezoelectric PTZT film produced by the process according to the third aspect on the orientation-controlled film of the substrate and drying the liquid composition, and the PTZT precursor film is calcinated and sintered, it is possible to form the piezoelectric PTZT film having a high orientation degree controlled to crystalline orientation of the orientation-controlled film.
• an electronic component having excellent piezoelectric properties and a long average breakdown time is obtained by using the piezoelectric PTZT film of the first or second aspect.
• a piezoelectric PTZT film which is the embodiment of the invention is a piezoelectric PTZT film in which a metal oxide having a perovskite structure including Pb such as lead zirconate titanate (PZT) is doped with Ta, and the content of carbon in the film is 80 to 800 ppm by mass as an average value.
• PZT lead zirconate titanate
• the content of carbon is greater than 800 ppm by mass, crystallinity is deteriorated, and thus, piezoelectric properties of the piezoelectric PTZT film are deteriorated.
• a preferable range of the content of carbon is 100 to 300 ppm by mass.
• the fraction of the Ta atoms in the piezoelectric film is in a range of 0 ⁇ Ta ⁇ 0.04, with respect to total metal atoms of Zr atoms and Ti atoms. When preparing a liquid composition which will be described later, so that the fraction of the Ta atoms in the piezoelectric film exceeds 0.04, a precipitate is easily generated in the solution at the time of preparation and storage.
• a preferable fraction of the Ta atoms in the piezoelectric film is in a range of 0.01 to 0.03.
• Ta atoms are not included at all, it is difficult to improve the piezoelectric properties of the piezoelectric PTZT film.
• the piezoelectric PTZT film according to the embodiment of the invention includes Pb, Ta, Zr, and Ti so as to have a predetermined metal atom ratio.
• the metal atom ratio (Pb:Ta:Zr:Ti) in the piezoelectric PTZT film preferably satisfies (0.99 to 1.04):(0.01 to 0.04):(0.40 to 0.60):(0.40 to 0.60).
• the fraction of Pb is smaller than the lower limit value, a large amount of pyrochlore phase is included in the piezoelectric PTZT film, and thus, electrical properties such as piezoelectric properties are significantly easily deteriorated.
• a Ta alkoxide, a Zr alkoxide, ⁇ -diketones, and a diol are refluxed to allow the Ta alkoxide and the Zr alkoxide to react with the diol, and thus, a first synthesis solution is produced.
• the Ta alkoxide and the Zr alkoxide are weighed so as to have fractions for applying the predetermined metal atom ratio in the piezoelectric PTZT film after forming the film.
• the weighed Ta alkoxide and Zr alkoxide are put into a reaction vessel and mixed with the ⁇ -diketones and the diol, and the components are preferably refluxed at a temperature of 130°C to 175°C in a nitrogen atmosphere for 0.5 to 3 hours to prepare the synthesis solution.
• an alkoxide such as tantalum pentaethoxide is used.
• the tantalum pentaethoxide is preferable because tantalum pentaethoxide is easily available, but reactivity is high and a precipitate is extremely easily generated. Accordingly, in the step of preparing the first synthesis solution, the Zr alkoxide, the Ta alkoxide, the ⁇ -diketones, and the diol are allowed to react with each other by refluxing at the same time, and thus, precipitation of the Ta alkoxide is prevented.
• an alkoxide such as zirconium-n-butoxide or zirconium-tert-butoxide is used.
• ⁇ -diketones stabilizer
• acetylacetone heptafluorobutanoyl pivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, or benzoylacetone
• acetylacetone is preferable, because acetylacetone is easily available.
• diol propylene glycol, ethylene glycol, or 1,3-propanediol is used.
• propylene glycol or ethylene glycol is preferable, because propylene glycol or ethylene glycol has low toxicity and an effect of increasing the storage stability is obtained.
• the diol is set as an essential solvent component, it is possible to set the content of carbon in the piezoelectric PTZT film in a predetermined range and to increase the storage stability of the liquid composition, by adjusting the amount of the diol added.
• a Ti alkoxide is added into the synthesis solution in the reaction vessel, while maintaining the temperature of the first synthesis solution, and the components are preferably refluxed and reacted with each other again in a nitrogen atmosphere for 0.5 to 5 hours to prepare the second synthesis solution.
• an alkoxide such as titanium tetraethoxide: Ti(OEt) 4 , titanium tetraisopropoxide: Ti(OiPr) 4 , titanium tetra n-butoxide: Ti(OnBu) 4 , titanium tetraisobutoxide: Ti(OiBu) 4 , titanium tetra t-butoxide: Ti(OtBu) 4 , or titanium dimethoxy diisopropoxide: Ti(OMe) 2 (OiPr) 2 is used.
• the Ti alkoxide is added in the step of preparing the second synthesis solution after the step of preparing the first synthesis solution, in order to increase the storage stability and prevent the generation of a precipitate, by allowing the Ta alkoxide and the Zr alkoxide to react with each other and promoting realization of a composite alkoxide.
• a step of preparing a third synthesis solution the second synthesis solution is cooled to room temperature by performing radiational cooling at room temperature, a Pb compound is added into the synthesis solution in the reaction vessel to further allow the refluxing and reaction, and thus, the third synthesis solution is prepared.
• a Pb compound acetate such as lead acetate: Pb(OAc) 2 or an alkoxide such as lead diisopropoxide: Pb(OiPr) 2 is used.
• the Pb compound is added in the step of preparing the third synthesis solution after the step of preparing the second synthesis solution, in order to prevent precipitation by allowing a reaction between the stable liquid composition including Ta, Zr, and Ti and the Pb compound to synthesize a composite alkoxide.
• the fourth synthesis solution is prepared by diluting the solution with alcohol.
• the solvent is removed from the synthesis solution by a method of atmospheric distillation or vacuum distillation, for example, and the liquid composition for forming a piezoelectric PTZT film according to the embodiment of the invention is prepared.
• alcohol ethanol, n-butanol, n-octanol or the like is used.
• concentration of the liquid composition after the dilution is 10 to 35 mass% and preferably 20 to 25 mass% in terms of oxide concentration.
• the concentration of the liquid composition is set to be in the range described above, because, when the concentration thereof is smaller than the lower limit value, sufficient film thickness is hardly obtained, and on the other hand, when the concentration thereof exceeds the upper limit value, cracks are easily generated.
• the oxide concentration of the concentration of the PTZT precursor occupying the liquid composition is a concentration of a metal oxide occupying 100 mass% of the liquid composition, which is calculated by assuming that all metal atoms included in the liquid composition have become the desired oxides.
• the diol in the liquid composition for forming a piezoelectric PTZT film according to the embodiment of the invention is added so that the content is 7 to 11 moles with respect to the total amount.
• the amount of the diol added is smaller than 7 moles, the content of carbon in the piezoelectric PTZT film is smaller than 80 ppm by mass, and when the amount thereof exceeds 11 moles, the content of carbon in the piezoelectric PTZT film exceeds 800 ppm by mass.
• the ⁇ -diketones (stabilizer) in the liquid composition for forming a piezoelectric PTZT film of the invention is added so that the content is 1.5 to 3.0 moles with respect to the total amount.
• the amount of ⁇ -diketones added is smaller than 1.5 moles, a precipitate is generated, and even when the amount thereof exceeds 3.0 moles, an effect is not changed.
• the diol in the liquid composition for forming a piezoelectric PTZT film is preferably added so that the content is 7 to 9 moles with respect to the total amount, but there is no limitation.
• the ⁇ -diketones in the liquid composition for forming a piezoelectric PTZT film is preferably added so that the content is 1.5 to 2.5 moles with respect to the total amount, but there is no limitation.
• the PTZT precursor included in the liquid composition for forming a piezoelectric PTZT film according to the embodiment of the invention is a raw material for configuring the metal oxide in the piezoelectric film after formation, and a Pb source, a Ta source, a Zr source, and a Ti source are included so that the metal atom ratio (Pb:Ta:Zr:Ti) in the piezoelectric PTZT film satisfies (0.99 to 1.04):(0.01 to 0.04):(0.40 to 0.60):(0.40 to 0.60).
• the Pb compound, the Ta alkoxide, the Zr alkoxide, and Ti alkoxide are weighed so that the metal atom ratio (Pb:Ta:Zr:Ti) in the PTZT precursor becomes (1.00 to 1.25):(0.01 to 0.04):(0.40 to 0.60):(0.40 to 0.60).
• the forming method is a method for forming a piezoelectric film by a sol-gel method, and the liquid composition for forming a piezoelectric PTZT film doped with Ta described above and containing carbon, is used as a raw material solution.
• the liquid composition for forming a piezoelectric PTZT film is applied onto a substrate, and a coated film (gel film) having a predetermined thickness is formed.
• the coating method is not particularly limited, and spin coating, dip coating, a liquid source misted chemical deposition (LSMCD) method, or an electrostatic spray method is used.
• LSMCD liquid source misted chemical deposition
• electrostatic spray method is used as the substrate where a piezoelectric film is formed.
• a silicon substrate where a lower electrode is formed or a heat-resistant substrate such as a sapphire substrate is used as the substrate where a piezoelectric film is formed.
• a lower electrode formed on a substrate is formed by using a material having conductivity and not reacting with a piezoelectric film, such as Pt, TiO x , Ir, or Ru.
• the lower electrode can have a double-layered structure of a TiO x film and a Pt film, in this order, from the substrate side.
• a TiO x film a TiO 2 film is used.
• a SiO 2 film can be formed on a surface of this substrate.
• orientation-controlled film in which crystalline orientation is preferentially controlled to the (100) plane, on the lower electrode where a piezoelectric film is formed, before forming the piezoelectric film.
• orientation-controlled film include an LNO film (LaNiO 3 film), a PZT film, or a SrTiO 3 film in which crystalline orientation is preferentially controlled to the (100) plane.
• the method disclosed in PTL 3 (hereinafter, referred to as the first method) is used, for example.
• an orientation-controlled layer is formed by applying a composition for forming a ferroelectric thin film onto the lower electrode of a substrate including the lower electrode having crystal plane oriented in the (111) axial direction and performing calcination and sintering of the composition.
• a crystal grain size controlling layer is formed on the lower electrode, and the applied amount of the composition for forming a ferroelectric thin film on the crystal grain size controlling layer is set so that a layer thickness of the orientation-controlled layer after crystallization is in a range of 35 nm to 150 nm and a temperature at the time of calcination is set to be in a range of 150°C to 200°C or 285°C to 315°C.
• this PTZT precursor film is calcinated, sintered, and crystallized.
• the calcination is performed under predetermined conditions by using a hot plate, a rapid heating process (RTA) or the like.
• the calcination is performed in order to remove a solvent and convert the metal compound into a composite oxide by pyrolysis or hydrolysis, and therefore, the calcination is desirably performed in the air, in the oxidation atmosphere, or in the atmosphere containing water vapor. Even when the heating is performed in the air, moisture necessary for hydrolysis is sufficiently ensured with moisture in the air.
• low temperature heating may be performed by using a hot plate or the like at a temperature of 70°C to 90°C for 0.5 minutes to 5 minutes.
• the calcination is performed by holding the temperature preferably at 250°C to 300°C for 2 to 5 minutes.
• a first stage is calcination in which the temperature is held at 250°C to 300°C for 3 to 10 minutes
• a second stage is calcination in which the temperature is held at 400°C to 500°C for 3 to 10 minutes.
• the calcination temperature in the first stage is preferably in a range of 250°C to 300°C, because pyrolysis of a precursor substance is insufficient and cracks are easily generated, when the calcination temperature is lower than the lower limit value.
• the calcination temperature exceeds the upper limit value, the precursor substance on the upper portion of the substrate is decomposed before the precursor substance in the vicinity of the substrate is completely decomposed, the organic matters remain around the substrate of the film, and the voids are easily generated.
• the calcination time in the first stage is preferably from 3 to 10 minutes, because the decomposition of the precursor substance does not sufficiently proceed, when the calcination time is shorter than the lower limit value, and the process time is increased and productivity may be decreased, when the calcination time exceeds the upper limit value.
• the calcination temperature in the second stage is preferably in a range of 400°C to 500°C, because residual organic matters remaining in the precursor substance are not completely removed and the film may not be sufficiently densified, when the calcination temperature is lower than the lower limit value.
• the calcination temperature exceeds the upper limit value, it may be difficult to control orientation properties due to promotion of the crystallization.
• the calcination time in the second stage is preferably from 3 to 10 minutes, because the residual organic matters are not sufficiently removed, and peeling or cracks of the film may be easily generated due to generation of strong stress at the time of crystallization, when the calcination time is shorter than the lower limit value. On the other hand, when the calcination time exceeds the upper limit value, the process time is increased and productivity may be decreased.
• sintering can finally be collectively performed after repeating the steps up to the calcination several times, so as to have a predetermined film thickness.
• the liquid composition according to the embodiment of the invention is used as the raw material solution, stress derived from film contraction generated at the time of forming a film can be prevented.
• a thick film having a thickness of approximately several hundreds of nm can be formed by a single coating step, without generating voids or cracks. Accordingly, the number of steps to be repeated described above can be decreased.
• the sintering is a step of sintering the PTZT precursor film after the calcination at a temperature equal to or higher than a crystallization temperature to perform crystallization, and a piezoelectric film is obtained by performing this step.
• a sintering atmosphere of this crystallization step O 2 , N 2 , Ar, N 2 O, or H 2 , or mixed gas thereof is suitable.
• the sintering is performed at 600°C to 700°C for approximately 1 to 5 minutes.
• the sintering may be performed by RTA. In a case of performing the sintering by the RTA, a rate of temperature rise thereof is preferably 2.5 to 100 °C/sec.
• a piezoelectric film having a greater thickness may be formed by repeating the steps from applying to sintering of the composition described above several times.
• the piezoelectric PTZT film is obtained. It is possible to improve a piezoelectric constant of this piezoelectric film by performing doping with Ta or including a predetermined amount of carbon. Thus, in the piezoelectric film, it is possible to obtain greater displacement and to decrease a dielectric constant. Accordingly, in a case of using this piezoelectric film as a sensor, the advantages are increased. One main reason thereof is considered that Ta added is substituted for Zr or Ti and cause oxygen deficiency.
• an electronic component such as piezoelectric micro electro mechanical systems (MEMS), an inkjet head, a mirror device, an autofocus, or a pyroelectric sensor is obtained.
• MEMS piezoelectric micro electro mechanical systems
• zirconium butoxide (Zr source), tantalum pentaethoxide (Ta source), acetylacetone ( ⁇ -diketones), and propylene glycol (diol) were put into a reaction vessel and mixed together. This mixture was refluxed in a nitrogen atmosphere at a temperature of 150°C for 0.5 hours, to prepare a synthesis solution. Titanium isopropoxide (Ti source) and acetylacetone were added to the obtained synthesis solution, and the synthesis solution was refluxed again at a temperature of 150°C for 0.5 hours, and cooled to room temperature.
• Lead acetate trihydrate (Pb source) was added to the obtained synthesis solution and the synthesis solution was refluxed again at a temperature of 150°C for 1 hour.
• the unnecessary solvent was removed by performing vacuum distillation, so that a concentration of the PTZT precursor occupying 100 mass% of the synthesis solution obtained by adding lead acetate trihydrate is 35 mass% in terms of an oxide concentration.
• dilution was performed with ethanol and the synthesis solution was diluted until the concentration thereof became 15 mass% in terms of an oxide concentration.
• Zirconium butoxide, tantalum pentaethoxide, titanium isopropoxide, and lead acetate trihydrate were respectively weighed and mixed with each other so that the composition of the synthesis solution after the dilution (liquid composition for forming a piezoelectric PTZT film) was PTZT (112/1/52/48).
• acetylacetone ( ⁇ -diketones) and propylene glycol (diol) were included in the liquid composition with fractions so that the content of acetylacetone ( ⁇ -diketones) was 2 moles with respect to the total amount and the content of propylene glycol (diol) was 7 moles with respect to the total amount.
• 1,000 ⁇ L of the liquid composition for forming a piezoelectric PTZT film was added dropwise onto the uppermost layer (orientation-controlled layer) of a 4-inched silicon substrate including an orientation-controlled layer configured with Pb 1.00 Zr 0.52 Ti 0.48 O 3 and having crystalline orientation preferentially controlled to (100) plane by the first method described above, and spin coating was performed at a rotation rate of 3,000 rpm for 15 seconds.
• the numerical values in the brackets are film thicknesses.
• the PTZT precursor film gel film which is a coating film was calcinated using a hot plate at 300°C for 3 minutes in the atmosphere. The operation from application to calcination of the liquid composition was repeated 4 times. After that, the temperature increased to 700°C by using the RTA at a rate of temperature rise of 50 °C/sec in the oxygen atmosphere, and the coating film was held at this temperature for 1 minute in the oxygen atmosphere, and accordingly, the precursor PTZT film was sintered. In addition, the operation from the applying to the sintering of the liquid composition was repeated 5 times, and a piezoelectric PTZT film was obtained.
• Liquid compositions for forming a piezoelectric PTZT film of Examples 2 to 8 were prepared in the same manner as in Example 1 and piezoelectric PTZT films of Examples 2 to 8 were obtained in the same manner as in Example 1, except that the fractions of the raw materials were changed as shown in Table 1.
• the liquid composition for forming a piezoelectric PTZT film 1,000 ⁇ L of the liquid composition for forming a piezoelectric PTZT film was added dropwise onto the PZT film (orientation-controlled film) of the uppermost layer of the 4-inched silicon substrate, which is the same as that in Example 1 and was set on a spin coater, and the spin coating was performed in the same manner as in Example 1.
• the PTZT precursor film gel film which is a coating film was calcinated using a hot plate at 75°C for 2 minutes in the atmosphere. Then, the PTZT precursor film was irradiated with ultraviolet light at 365nm for 5 minutes.
• the temperature increased to 700°C by using the RTA at a rate of temperature rise of 50 °C/sec in the oxygen atmosphere, and the coating film was held at this temperature for 1 minute in the oxygen atmosphere, and accordingly, the precursor PTZT film was sintered.
• the operation from applying to sintering of the liquid composition was repeated 19 times, and a piezoelectric PTZT film was obtained.
• Comparative Example 1 by performing the irradiation with ultraviolet light after the calcination, organic matters in the film were decomposed, the amount of residual carbon decreased, and a piezoelectric film having a small carbon content was obtained.
• Liquid compositions for forming a piezoelectric PTZT film of Comparative Examples 2 and 3 were prepared in the same manner as in Example 1 and piezoelectric PTZT films of Comparative Examples 2 and 3 were obtained in the same manner as in Example 1, except that the fractions of the raw materials were changed as shown in Table 1.
• Table 1 shows the metal atom ratio in the liquid compositions for forming a piezoelectric film prepared in Examples 1 to 8 and Comparative Examples 1 to 3, the molar quantity of diol, and the molar quantity of ⁇ -diketones.
• Example 1 1.12:0.01:0.52:0.48 7 1.5
• Example 2 1.13:0.02:0.52:0.48 7 2.0
• Example 3 1.12:0.01 :0.40:0.60 7 2.0
• Example 4 1.14:0.03:0.52:0.48 7 2.0
• Example 5 1.14:0.025:0.52:0.48 8 2.0
• Example 6 1.15:0.04:0.52:0.48 11 2.0
• Example 8 1.12:0.01:0.52:0.48 7 3.0 Comparative Example 1 1.14:0.03:0.52:0.48 6
• the film thickness, the film composition, the content of carbon in the film, the fraction of the Ta atoms with respect to the total amount of the metal atoms of Zr atoms and Ti atoms in the film, the piezoelectric constant, the average breakdown time, and the orientation degree to (100) plane were respectively evaluated by the following methods. The results thereof are shown in Table 2.
• the piezoelectric film of Comparative Example 1 includes Ta, but the content of carbon was as low as 30 ppm by mass.
• the piezoelectric constant d 33 was as low as 110 pm/V and the average breakdown time was significantly as short as 6.44 ⁇ 10 3 seconds.
• the piezoelectric film of Comparative Example 2 does not include Ta and has low carbon content of 50 ppm by mass.
• the piezoelectric constant d 33 was significantly as low as 87 pm/V and the average breakdown time was as short as 1.08 ⁇ 10 4 seconds.
• the piezoelectric film of Comparative Example 3 includes Ta, but the content of carbon was as high as 820 ppm by mass.
• the piezoelectric constant d 33 was as low as 103 pm/V, even though the average breakdown time was as long as 1.83 ⁇ 10 4 seconds.
• the content of carbon was in a range of 80 to 800 ppm by mass and Ta was included.
• the piezoelectric constant was high, the average breakdown time was long, and the (100) plane orientation degree was as high as 92% to 99%, compared to those in Comparative Examples 1 to 3.
• the piezoelectric PTZT film of the invention can be used in electronic components such as piezoelectric micro electro mechanical systems (MEMS), an inkjet head, a mirror device, an autofocus, or a pyroelectric sensor.
• MEMS piezoelectric micro electro mechanical systems

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